Electrical capacitance tomography (ECT) is a technique used to determine the dielectric permittivity distribution in the interior of an object from external capacitance measurements. ECT enables insight into the material distribution within a closed vessel, and consequently, into the governing mechanism in processes occurring within the vessel, without disturbing the processes themselves.
The basic procedure of AC-based capacitance measurement is to apply a sinusoidal voltage signal to an electrode (that forms one plate of a capacitor) and measure the output current/voltage on another electrode (that forms the other plate of the capacitor), from which the capacitance is determined. An existing method, referred to as MECaP (multiple excitation capacitance polling), applies multiple excitation signals to multiple electrodes at each time instance, thereby enabling simultaneous measurement of more than one inter-electrode capacitance from a single receiving electrode. MECaP is limited in that it can only read a single receiving electrode during each step. MECaP increases the measurement speed relative to the traditional single excitation/single receiver system that has been utilized for the past decade. However, in some time-sensitive applications the increased speed is still inadequate for capturing high speed dynamics, which is the intended use of the ECT system.